Effect of different whey protein to casein ratio and fat content on thermal denaturation of whey proteins

In the process of fermented milk products, heat treatment is an important step leading to whey protein denaturation and significant changes in their functional properties. Denatured whey proteins, within gels made from heated milk, are important for increased stiffness of yogurt gels. Therefore, in this study the effects of different whey protein to casein ratio from 0.22 (in native skim milk) to 0.46 and 0.70 and fat content (0.5, 1.0 and 1.5%) on thermal denaturation of whey proteins, at 85‐ for 15 minutes, were studied. The insoluble protein nitrogen in the mixes was precipitated before and after heating. The soluble nitrogen was measured by semi-micro Kjeldahl method and the extent of whey protein denaturation, occurring in the mixes during the heat treatment, was calculated. The results showed that whey protein to casein ratio has significant effect (P